CBS This Morning

BRUSSELS When the armored van set off for Brussels airport carrying $50 million worth of precious stones from Antwerp's high-security diamond district, eight robbers knew exactly what was up.

One of the biggest diamond heists of recent memory was about to go down.

The Belgian port city of Antwerp is the world capital of diamond-cutting. Over the years, the city's close-knit diamond community has created one of Europe's most secure zones, with some 2,000 surveillance cameras, police monitoring and countless identity controls to protect its $200 million in daily trade of rough and polished gems.

Antwerp, which lies 27 miles from the airport, had been hit by a major heist in 2003 and had learned its lesson.

"We are just about the safest place in Belgium," said Antwerp World Diamond Center spokeswoman Caroline De Wolf.

And once Swiss Flight LX789 was airborne Monday night on its way to Zurich, a cache of diamonds tucked safely in its hold, that would not be a great place for a robbery either.

But the airport's 25-kilometer perimeter fence and the transfer of the diamonds from the security van on the tarmac to the hold of the Fokker 100 twin engine jet - now that held potential.

Bingo.

After weeks of lashing rain, snow, sleet and black ice, Monday evening was finally was as good as it gets in late winter in Belgium. Crisp, cold air meant dry roads for a perfect getaway, and winter's early darkness was a blessing for those needing stealth.

About 20 minutes before the flight's planned 8:05 p.m. departure, the robbers used a construction site outside the airport fence in which to hide. Then in two black cars with blue police lights flashing, they forced their way through the fence and onto the tarmac, speeding straight to pier A.

That was right where the armored car had just finished transferring the diamonds into the Fokker.

Dressed in dark police clothing and hoods, the thieves halted by the plane, whipped out machine guns and stopped the pilots and the transport security crew in their tracks.

The 29 passengers?

"They saw nothing," Anja Bijnens of the Brussels prosecutor's office said Tuesday. "They never fired a shot. They never injured anyone."

With speed and precision, the thieves opened the plane's hold, picked out 120 parcels and loaded them into the cars.

"Afterward, they made a high-speed getaway," Bijnens said, estimating the whole operation took about five minutes.

By late Tuesday, investigators had found the charred remains of a van most likely used in the heist but little else.

Behind them, the robbers left embarrassed airport officials trying to explain how thieves could so smoothly get into the airport, stage a robbery and make a clean getaway. Diamond industry officials who pride themselves on the security of their trade were equally mortified.

Airport spokesman Jan Van Der Cruijsse could not explain how the area could be so vulnerable - not only to theft, but possibly to terrorism.

"'We abide by the most stringent rules," he said, noting the same apply to other European airports. "It has always been clear we meet all the requirements."

Philip Baum, an aviation security consultant in Britain, called the robbery unsettling - not just because the fence was breached, but because the response did not appear to have been immediate. That, he said, raised questions as to whether alarms were ringing in the right places.

"It does seem very worrying that someone can actually have the time to drive two vehicles onto the airport, effect the robbery, and drive out without being intercepted," Baum said, raising the specter that terrorists could exploits such lapses as well.

Air transport is considered the safest way of transporting small high-value items, logistics experts say, a fact reflected by relatively cheap insurance policies.

Unlike a car or a truck, an airplane is unlikely to be waylaid by robbers once it has taken off. It's also considered to be very secure before the departure and after its arrival because the aircraft is always within the confines of an airport, which are normally highly secured areas.

The parcels contained rough and polished stones heading for Switzerland, where many of the 120 parcels were intended for different handlers.

"What we are talking about is obviously a gigantic sum," De Wolf said, giving an estimate of $50 million.

A decade ago, Antwerp was hit by one of the biggest diamond heists in history, when robbers disabled an alarm system and took precious stones, jewels, gold and securities from 123 of the 160 high-security vaults at Antwerp's Diamond Center. The loot was so abundant that the thieves even had to even leave some of it behind, police said, estimating the 2003 robbery to be worth about $100 million at the time.

Monday's heist, though, was a fresh blow to Antwerp's major industry, which prides itself on discretion and security.

"This is causing quite some unrest," said De Wolf. "It was incredible how easily it all went. This is worrying in terms of competitiveness, since other diamond centers are ready to pounce and take over our position."